The proposed research is aimed at determining cellular transmembrane pH gradients by non-invasive, continuous measurement using nuclear magnetic resonance. This, in part, entails the development of more sensitive, 19F NMR methodologies and indicators. Additional fluorinated amino acids and their esters will be synthesized and tested in order to find optimal indicators and indicator precursors for measuring organelle and cytosolic pH under physiologic conditions. As these methods are developed we will apply them to measurements of cytosolic and compartment pH in situ (human blood lymphocytes, isolated rat hepatocytes and cloned insulinoma cells), in order to study the relationship between cytosolic pH and compartment pH, metabolic and developmental processes.